I'm in the process of converting the D-Jetronic in my 71 142 to twin Weber 45 DCOE carburetors. I have ran into a frustrating problem that I hope people in the forum could give me some direction.

The problem is that the rear intake manifold will not clear the headers. I tried two different headers: a BHP and a IDP. Both interfere at different header tubes. Not by a lot but enough to prevent the installation. The only one that worked was the stock cast iron intake manifold, which I'd rather not use. I do not believe this has to do with the intake manifold but by the way the tubes in the headers are routed.

Does anyone know of a header that works with the Weber DCOE carbs?

Thank you in advance.

I'd like to see a picture of those BHP headers and if you are putting Twin 45DCOE's on a 140, the intake HAS to be a copy of Volvo's as it is the correct length & flows the best AND should clear any exhaust header.

no text.

How big is your cam?

The stock 3-2-1 cast iron exhaust manifold works just fine up until you need 4-1 style headers.

Up until you go bigger than 240° @ .050" & 110°LSA, you want headers that work a little bit everywhere since you have built a motor that should take full throttle from idle in top gear.

Cheers,
Paul.

There are several different intake manifolds out there, and each comes with its own clearance issues. Maybe it would be easier to use a different intake than look for a different header.

The ipd header won't improve performance, regardless.

Which intake are you working with?

Cameron
Portland

Thanks for the response Cameron. The particular intake manifold that I have was made by IMW. The interference with the header tubes is in the flanges, where the carb bolts to the intake manifold. The flanges follow the contour of the carbs. I do not believe the problem is with the intake manifold.

At this point I'm leaning towards using the stock FI cast iron exhaust manifold, which clears the intake manifold with room to spare. Unfortunately I have only the manifold. Not the downpipe. At the moment, none of the suppliers that I called has a downpipe in stock and I was told months away from getting one. So I'm in search for a used one.

Have you tried Mike Dudek at iRoll Motors?

I'm not familiar with the imw manifolds, so I can't offer much insight there.

The easiest fitting manifold I've used is the Mangoletsi.

Bottom line, though, is that whatever you use will require some measure of modification to get everything working together.

Cameron
Portland

https://www.ebay.com/itm/124953294636?hash=item1d17cbf72c:g:2QIAAOSwQ75haDDo&amdata=enc%3AAQAHAAAAoEhWyYJ2HMVazoEUuQ5Res5yHyLSD59O5UjEFET55Zuqd6IMJFScghC%2FSe3FITapUf4pS8EyQJ6tWujkTzevvp9Lk5Z53xZqzkx4C9NpLmYeBFsOylpswP6mG%2F9kmkyqGdcOVGV4LghW8Jp8ns3ktwMYTTQTCy0gsHZFkrYoCJ4Mh20lqbJRNWhsFCh8d07SJeUMBJLQk42OC4DE6gDZesg%3D%7Ctkp%3ABk9SR6y82-zCYA

https://www.rendcarparts.com/volvo/parts/462570-684198/RD462570A

the stock injection manifold was listed in the rsport catalog for stage 3 and 4 engine upgrades. they do say to extend each down pipe 4 inches before merging into 1 pipe. there was a long branch header also but finding 1 now is impossible.

I was not aware that the cast iron stock FI manifold had performance potential.
I assume we are talking about this:
https://classicvolvorestoration.com/product/exhaust-manifold-volvo-b20ef-1970-74/

page 16 https://people.physics.anu.edu.au/~amh110/R-Sport/R-Sport_Catalog_1979.pdf

Thank you porkface. I believe it is what I have. It is an option. Even though I would prefer to keep the current BHP header if it could be modified to fit.

It is not unusual to have to modify either the intake or exhaust manifold flanges for clearance.

It also not unusual to have to make special washers for the 4 studs where the intake and header meet.

Can you post pictures of the intake manifolds?

--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Hi Eric. I have no idea how to post pictures on this forum.
There is nothing special about the intake manifold. It is like any other you have already seen. Same for the exhaust headers. Independently both bolt on the the head fine. The problem is when the headers are bolted on to the head, there is no room between the tubes in the headers to fit the rear intake manifold. It is just the routing of the header tubes that causes the problem. Whoever designed them, did not consider that they could be used together with DCOE Webers.

I'm trying to find out if anyone on the forum knows of a header that works together with the DCOE Webers. As I said, if nothing comes up, I will either try to modify the BHP header that I have or use the cast iron FI exhaust manifold that I know fits. Both options will be challenging, as my welding skills are terrible and finding a competent welder around here is almost impossible.

Can this be overcome by some grinding of the exhaust flanges? They may look fine but finding a set which works better than the cast iron one is difficult. That one works fine up to about 150bhp so the engine has to be in a high state of tune for that. Twin Webers don't automatically guarantee a massive boost in power. Again, they do look good though.

Thank you Derek for the reply. The exhaust flanges fit fine. The problem is the in routing of one (different) tube in each of the headers. If all else fail, I may try reroute one of them.

I prefer not to use the stock intake manifold because it has several hairline cracks on the inside that I suspect will grow over time.